Recent improvements in construction materials and techniques have given rise to the widespread usage of plastic piping. Such piping has proven to be especially useful as conduit for the protection of undergrounded electrical wiring, as drain pipe, etc.
In many applications, such pipe is formed in predetermined lengths and placed end-to-end in a trench and a connector is placed over the ends so as to join the pipes together.
In a large number of applications, on the other hand, the adjacent pipe lengths may be joined by slipping the end of one length into the end of the adjoining length. This can be accomplished if the adjoining length is formed with an enlarged or belled end of such a size as to receive the end of the first length.
In the past, the provision of a belled end on a length of plastic pipe was a time consuming, cumbersome, and costly operation since each individual length of pipe had to be manually moved from the pipe extruder to a heater and then to a belling machine. Thus, a workman had to be in position to maneuver each piece of pipe throughout the operation.
Recently, machinery has been developed to eliminate the handling of the individual pipe lengths during the operation. However, this machinery is manufactured with the various elements in fixed relation to one another, so that it is very difficult to adjust the machine for the production of different finished lengths of pipe.
As a major disadvantage of these machines, only one piece of pipe length can be handled at a time and, when that time span is completed, the piece of pipe is dumped from the machine, whether or not the operation is completed. As a result, the timing of each of the operations conducted by the machine is extremely critical and little or no leeway is available.
Also in these machines, a heater mandrel is provided which extends into the pipe and heat band is positioned above the exterior of the pipe so as to soften it for belling. When pipe diameter is to be changed, the heater coils on the inside and outside of the pipe must be disconnected and a new set installed. Since the clearance between the internal heating mandrel and the pipe is necessarily small in these machines, the clamping units which hold the pipe in place during heating often cause it to come into contact with the internal mandrel, resulting in burning the internal surface of the pipe wall.
In summary, when finished lengths of plastic pipe were to be belled and otherwise suitably prepared for use, in accordance with the teachings of the prior art, each length of pipe had to be physically moved and handled by a laborer between the operating stations, or a machine had to be used which was difficult to adjust for various lengths and diameters of pipe, was subject to a critical timing factor, and could easily damage the internal surface of the pipe.